WO2012006626A2

WO2012006626A2 - Flow controller

Info

Publication number: WO2012006626A2
Application number: PCT/US2011/043575
Authority: WO
Inventors: Todd M. Ulschmid; John G. Fisher; Jorge A. Diaz; Wiley J. Wilkinson; Christopher M. Belsky; Robert T. Chinnock; Robert K. Snyder
Original assignee: Entegris, Inc.
Priority date: 2010-07-09
Filing date: 2011-07-11
Publication date: 2012-01-12
Also published as: TW201234155A; WO2012006626A9; WO2012006626A3

Abstract

A flow controller includes a body having an inlet end, an outlet end, a flow measurement portion, a variable valve portion and a control portion to control the valve portion based on an output from the flow measurement portion. The flow measurement portion includes a pair of differential pressure sensors for measuring the pressure drop across a flow path as the fluid flows through the flow path. The flow control portion comprises a flexible tube and a plunger with a motor drive that incrementally pinches the flexible tube. A linear, constant diameter bore extends through the housing forming a fluid flow passage for providing a calibrated pressure drop to a fluid that is passed through the fluid flow passage. A replaceable portion of the fluid flow passage is comprised of resilient soft plastic tubing as part of a pinch valve having non-contaminating fittings for positive device shut off.

Description

FLOW CONTROLLER

Related Application

The present application claims the benefit of U.S. Provisional Application No. 61/362,882, filed July 9, 2010.

Field of the Invention

The present invention relates to flow controllers. More particularly, the present invention relates to a flow controller having a constant diameter flow path between a pair of sensors and a variable valve portion.

Background of the Invention

Flow controllers combine flow measurement and variable valve metering to provide a desired volumetric and/or mass flow rate. Typically, the flow is measured by a pair of pressure sensors with a narrowing of the flow conduit intermediate the two pressure sensors, defining an orifice; the pressure drop across the restriction is measured and the flow rate can be calculated therefrom. For many applications, particularly involving uniform density fluids, this is a very satisfactory configuration.

In some applications involving slurries, this arrangement is not ideal. A chemical mechanical polishing (CMP) apparatus is production equipment used in a planarization process of a semiconductor device that chemically and physically polishes a surface of a semiconductor wafer using slurry including a polishing agent and a polishing pad rotating together with the slurry.

Dispensing of the slurry material to a platen of a chemical-mechanical polishing (CMP) tool from a delivery module is typically controlled by timed flow of material at a rate that is generally assumed to be constant. It is important that the flow rate of the slurry delivered to the device remain controlled and constant. Uneven flow rates over time can lead to inaccurate dispensing of CMP slurry to the platen. Often, this problem is addressed by utilizing an overly high flow rate to ensure that ample slurry is present on the platen. However, oversupply of CMP slurry needlessly increases the cost of the process by consuming excessive slurry material. This problem is exacerbated by the short lifetime of mixed slurry, which requires that the slurry be consumed shortly after its preparation from individual components

In order to maintain a controlled flow rate, most CMP apparatuses typically utilize a flow meter for controlling the flow of slurry at a predetermined rate. Such flow meters utilize restricted orifices to provide a pre-calibrated pressure drop to the slurry or utilize right angle turns (elbows) in the flow path. However, such restricted orifices and elbows can result in additional undesired changes to flow velocities and create areas of flow stagnation where slurry may accumulate. Such can create inconsistency and inaccuracies in the flow control.

It would therefore be desirable for there to be a flow controller that can provide for a steady, predetermined flow rate of slurry while minimizing the above-described problems.

Summary of the Invention

A flow controller includes a body having an inlet end, an outlet end, a flow measurement portion, a variable valve portion and a control portion to control the valve portion based on an output from the flow measurement portion. A desired flow rate is provided to the control portion. The flow measurement portion includes a pair of pressure sensors for measuring the pressure drop across a flow path as the fluid flows through the flow path. The flow control portion comprises a flexible tube and a plunger with a motor drive. The plunger incrementally pinches the flexible tube. A linear, constant diameter bore extends through the housing, particularly forming a fluid flow passage or conduit for providing a calibrated pressure drop to a fluid that is passed through the fluid flow passage between the flow measurement sensors. A replaceable portion of the fluid flow passage is comprised of resilient soft plastic tubing as part of a pinch valve having non-contaminating fittings for positive device shut off. The housing can include a removable portion allowing access to the pinch valve and pinch valve fittings, such that they are field repairable without specialized tools.

In certain embodiments, the flow controller is comprised principally of a body portion formed of a generally rectilinear block of fluoropolymers material, such as PTFE, the body portion having a pair of recesses extending downwardly for placement of transducer units and defining chambers or cavities for the fluid to be measured, a portion adapted for receiving variable valve components, and a conduit extending lengthwise therethrough connecting the cavities. Variable valve components may comprise a flexible tubing segment, the tubing segment attachable to a pair of connections, one connection at a conduit leading to the pair of recesses, the other leading to an exit conduit. The variable valve components may include a stepper motor with a linear output, a support portion for the central portion of the tube, and a plunger to variably pinch the tube.

In one embodiment, a continuous constant diameter bore extends between the pair of pressure transducers. In another embodiment, the flow conduit to a first transducer is of a first diameter, the flow conduit between the first transducer and a second transducer is of the first diameter, and the flow conduit between the second transducer and the variable valve portion is of the first diameter.

A feature and advantage of embodiments of the present invention is smooth continual flow velocity. The linear, constant diameter flow path eliminates the restricted orifices and elbows of the prior art, therefore minimizing the opportunities for undesired disruptions of the flow velocity of slurry traveling through the flow controller, particularly intermediate the pressure sensors. In embodiments, the diameter of the flow passage between the pressure sensor chambers constant within 2 percent of the largest diameter of the flow passage. In embodiments, the diameter of the flow passage between the pressure sensor chambers constant within 5 percent of the largest diameter of the flow passage. In embodiments, the diameter of the flow passage between the pressure sensor chambers constant within 8 percent of the largest diameter of the flow passage.

Moreover, the elimination of restriction orifices and/or elbows minimizes the possibility of stagnation and entrapment of slurry as it flows through the device.

A further feature and advantage of embodiments of the present invention is a field repairable pinch valve. The housing can include a removable portion that allows direct access to the pinch valve and pinch valve fittings and the valve fittings can be non-contaminating, allowing the valve to be cleaned, repaired, maintained, and/or replaced without the use of special tools.

Another feature and advantage of embodiments of the present invention is positive shut off of the flow path. The pinch valve allows the flow path to be completely shut off such that no slurry is allowed to travel along the flow path.

An additional feature and advantage of embodiments of the present invention is highly accurate flow rate control. By minimizing flow velocity disruptions and slurry stagnation and entrapment, the present invention allows for highly accurate, pre-calibrated flow rate control.

Additional features and advantages of embodiments of the invention relate to the minimal number of connections between components forming the flow controller. In an embodiment, a first connector that connects to an external fluid flow tubing or the like, is integral with a body portion that has a bore defining a channel extending between the first connector and a first sensing chamber. The first sensing chamber is within and defined by the body portion. A further bore, within and defined by the body portion leads to a second sensing chamber, within and defined by the body portion, a further bore within and defined by the body portion extends from the second sensing chamber to a further connector portion that receives one end of an first internal pinchable tubing connector. The other end of the pinchable tubing attaches to a second pinchable tubing connector that is integral, that is unitary, with a second external connector for connection to external fluid flow tubing. Thus the connections that form the fluid flow path within the flow controller are only the two internal pinchable tubing connectors. The connectors, in particular embodiments, are field disconnectable from the pinchable tubing allowing easy field replacement of the pinchable tubing that functions as the variable valve in the flow controller.

In related embodiments, the two internal pinchable tubing connectors may be intermediate the two sensing chambers with one or both of the internal tubing connectors integral with the same body portion or with two different body portions. That is, each sensing chamber may be in a separate body portion with the flexible tubing extending therebetween. Each body portion can define an external connector and an internal connector, the external connectors to connect to tubing for putting the flow controller in a fluid system and the internal connectors for the flexible pinchable tubing This maintains the minimal number of internal connections defining the fluid flow path at two.

A further feature and advantage of embodiments of the present invention is that it provides for field calibration to accommodate various slurries or other fluids with a wide range of densities and viscosities. The device can include embedded firmware and can also be used with a stand-alone computer calculation tool that allows a user to calibrate the device to provide for a desired flow rate for a variety of different slurry mixtures. Brief Description of the Drawings

Figure 1 is a perspective view of a flow controller according to an embodiment of the present invention.

Figure 2a is an exploded view of the flow controller of Figure 1.

Figure 2b of a flow controller according to an embodiment of the present invention. Figure 3 is a cross-sectional view of the flow controller of Figure 1 taken along the line

3-3.

Figure 4 is a cross-sectional view of a flow controller according to an embodiment of the present invention.

Figure 5 is a cross-sectional view of a flow controller according to an embodiment of the present invention.

Figure 6 is a perspective view of a flow controller according to an embodiment of the present invention.

Figure 7 is a screen shot for a field calibration tool that can be used with a flow controller according to an embodiment of the present invention. Figure 8 is a screen shot for a field calibration tool that can be used with a flow controller according to an embodiment of the present invention.

Figure 9a is a cross-sectional view of a flow controller according to an embodiment of the present invention.

Figure 9b is a partial cross-sectional view of the flow controller of Figure 9a.

Detailed Description of the Drawings

Referring to Figures 1-3, there can be seen a flow controller 100 according to an embodiment of the present invention. Flow controller 100 includes a main body portion 102 between a bottom plate 104 and a top cover 106. Flow controller 100 generally comprises a flow measurement portion 107, a variable valve portion 108 with a motor assembly 1 10, and a control portion 1 1 1. The control portion can comprise a circuit board 112 connected to top cover 106 and a cover seal 1 14 can be positioned adjacent main body portion 102.

Main body portion 102 can include a fluid flow passage 1 16 extending therethrough. In one embodiment, the fluid flow passage 1 16 is a bore defined through the main body portion 102. Fluid flow passage 1 16 can have a constant diameter and can extend through a connector 1 18 that can act as a fluid inlet or outlet on one end of main body portion 102. An intermediate connector 120 can connect fluid flow passage 1 16 to variable valve portion 108. Variable valve portion 108 can then include another connector 122 that can be a fluid inlet or outlet positioned at an opposite end of main body portion 102 such that a fluid receiving device can be connected to one of the connectors 1 18, 122 and a fluid source can be connected to the other of the connectors 1 18, 122 to provide for a flow of fluid through main body portion 102.

Main body portion 102 can also include a pair of sensor apertures 124 extending into fluid flow passage 1 16. Sensor apertures are adapted to contain pressure sensors 126 for sensing a pressure drop in a fluid flowing through fluid flow passage 1 16. The pressure sensors when in place in the apertures define sensor chambers 127 in the body portion. In one embodiment, pressure sensors 126 can be pressure transducers with sapphire plates. In other embodiments, various other pressure sensors can be used. Also the flow measurement portion can comprise ultrasonic sensors and any other types of sensors that can be used to determine the flow of a fluid. The fluid flow passage 1 16 and pressure sensors 126 define the flow measurement portion 107 of flow controller 100. Main body portion 102 can also include a pinch aperture 128 extending through a portion of the body through which a portion of the motor assembly 1 10 can extend. Main body portion 102 can further include a removable portion 130. Removable portion 130 can be affixed to main body portion 102 with screws or other fasteners when flow controller 100 is in operation. If maintenance or replacement of variable valve portion 108 is needed, removable portion 130 can be easily separated from main body portion 102 to allow access to variable valve portion 108. Secondary body portion 103 can include an internal connector 107 and an external connector 109. In certain embodiments, the internal connector and external connector may be integral or unitary with the main body portion. That is, each of the two internal connectors and the two external connectors and the two sensor chambers and the fluid passage between the chambers are all part of and in a single body.

Variable valve portion 108 can include the connector 122, a tubing portion 132 and a pair of retaining nuts 134, 136. Tubing portion 132 can include a hollow flow path 133 therethrough and can be connected to a fitting on connector 122 with retaining nut 134 and connector 120 with retaining nut 136 so that flow path 133 of tubing portion 132 is in fluid communication with fluid flow passage 1 16. Flow path 133 through tubing portion 132 can have the same constant diameter as fluid flow passage 1 16. In one embodiment, tubing portion 132 comprises an elastomeric material. Connector 122 can include a rounded portion 138 having a plurality of projections 140 that mate with corresponding apertures 142, 144 in arched portions 146, 148 of main body portion 102 and removable portion 130 to retain connector 122 between main body portion 102 and removable portion 130.

Motor assembly 1 10 can include a motor 150, a spacer 152 and a tubing pincher configured as a plunger 154. In one embodiment, motor 150 can be linear actuator stepper motor, such as provided by Haydon Switch & Instrument Inc. of Waterbury, CT and disclosed in U.S. Patent No. 6,603,229. Spacer 152 can be used to displace motor 150 and plunger 154 a desired distance above variable valve portion 108. Plunger 154 extends through pinch aperture 128 and can be moved longitudinally up and down by motor 150.

Variable valve portion 108 and motor assembly 1 10 can cooperate together to provide a pinch valve that acts as a flow control portion for flow controller 100. In normal operation, fluid can flow freely through tubing portion 132 of variable valve portion 108. To decrease or eliminate the ability of fluid to flow through tubing portion 132, motor 1 10 can be activated with an electronic control portion. Upon activation of motor 150, the plunger 154 is moved longitudinally downward to engage the tubing portion 132 against anvil 156 of removable portion 130. Flow path 133 through tubing portion 132 can be completely closed with plunger 154 to eliminate all flow through flow path 133, or can be only partially closed such that fluid can flow through at a decreased rate.

In operation, flow controller 150 is connected in-line in any type of processing application to provide a measured flow control to a variety of fluids. In one embodiment, the processing application is chemical mechanical polishing of substrates and the fluid is polishing slurry. A fluid enters flow controller through connector 1 18 or connector 122 and flows through the device out the other connector 1 18, 122 to the next step in the process. The pressure drop of the fluid flowing through the device is measured by the pressure sensors 126 in the flow path 1 16. In one embodiment, the flow passage 1 16 through the main body portion 102, the flow path through the tubing portion 132 and all fittings and connectors can have the same, constant diameter. In an embodiment they have a constant diameter within 10 per cent of each other. This provides for smooth, continuous velocity flow for the fluid with minimal areas for flow stagnation and entrapment. In another embodiment, the diameter of the flow passage 1 16 between the pressure sensors 126 is constant, but the diameter of the flow paths 1 16, 133 may vary at other locations. The flow of the fluid can be reduced or stopped as desired, based on feedback from the pressure sensors 126, by activating motor 150 to engage tubing portion 132 between plunger 154 and anvil 156.

Figure 4 depicts a cross-sectional view of another embodiment of a flow controller 101 according to an embodiment of the present invention that is similar to flow controller 100 depicted in Figures 1-3. In this embodiment, a portion 1 17 of the flow passage 1 16 has a wider diameter than the constant diameter flow paths 1 16, 133 of the main body portion 102 and tubing portion 132. The measurement interface or cavity between flow passage 1 16 and pressure sensors 126 as defined by sensor apertures 124 in flow controller 101 is also more rounded and does not extend completely through the flow passage 1 16. Figure 4 also depicts a connector 158 and a cord 160 for connecting the electronic and control systems of a flow controller with an outside source.

Referring now to Figure 5, there is depicted a flow controller 200 according to another embodiment of the present invention. Flow controller 200 includes a housing 202 with a flow path 216 extending therethrough and a pair of pressure sensors (not pictured) positioned in sensor apertures 224 for measuring a pressure drop of a fluid flowing through flow path 216. A tubing portion 232 comprised of an elastomeric material is positioned between the sensor apertures 224 and can be connected to the flow path 216 with connectors 234. A flow path 233 through tubing portion 232 can have the same diameter as some or all of the flow path 216. The flow of fluid through tubing portion can be controlled by use of stepper motor 250. When stepper motor 250 is actuated, plunger 254 can move longitudinally downward to pinch tubing portion 232 against anvil 256 to restrict or prevent flow of fluid through tubing portion 232.

Figure 6 depicts another flow controller 300 according to an embodiment of the present invention. Flow controller 300 includes pressure sensors 326 contained within separate sensor housings 325. Rather than the flow path 316 between the sensors 326 being defined by a bore through a housing, in this embodiment the flow path 316 is defined by a section of tubing 315 extending between the sensors 326 and connected to the sensor housings 325 with connectors 335. Tubing 315 can be flexible tubing or non-flexible tubing. A pinch valve assembly and motor assembly, as described herein, may be contained within housing 309 for variable control of fluid flow through flow controller 300.

Flow controller can be calibrated in the field with the use of a software system before being activated to provide a desired pressure drop to a fluid that will be allowed to flow through the flow controller. Field calibration provides the advantages of adjusting the flow controller for fluids having a wide range of densities and viscosities. Figures 7 and 8 depict screenshots of one example of such a software system. To calibrate the flow controller, flow data is collected for a given set of values and calibrated coefficient values are determined. Preferably, flow data is measured in the native environment of the flow controller so that conditions such as fluid temperature and line pressure will be consistent with field conditions. Flow data can be collected in various units, such as, for example, %FS, mA, or VDC. As shown in Figure 7, flow data can be collected at every 10% interval between 10% and 100% FS. For each interval, flow data is preferably collected for at least one minute, and then the flow data is entered for each interval in, for example, ml/min into the calibration data file shown in Figure 7. The flow controller should be rezeroed before each subsequent interval at which data is collected. As the data is collected, a graph of fit quality can be displayed and a set of coefficients that will provide the desired pressure drop is determined by an internal formula as shown in Figure 7. Once the data is visually inspected to ensure there are no clear errors, the data can be copied to a clipboard for use in the field calibration tool, which can be seen in Figure 8.

Once the flow rate data is acquired, the field calibration tool depicted in Figure 8 is then opened and the flow controller is connected to a device, such as a computer or mobile phone, operating the software. The settings menu item can be used to select the port to which the flow controller is connected and the software system and the flow controller can then be communicatively connected. Proper communication between the software and the flow controller can be verified in the "Model String" table. The calibration values currently in the flow controller will be displayed in the "Current Values" table for reference. The new calibration values can then be imported into the software from the clipboard into the "New Values" table. The device can then be configured with the new calibrated values by selecting the "Write field calibration to device" button. The flow controller has now been calibrated to provide the desired flow output. Figures 9a and 9b depict a flow controller 100B according to another embodiment of the present invention. The flow controller 100B depicted in Figures 9a and 9b is similar to the flow controller 100 described previously, but includes a positive stop feature to prevent over- compression of the tubing portion 132. Positive stop feature incorporates a plunger 154 having a flange 155 and a plunging portion 161 and an anvil 156 in removable portion 130. As can be seen in Figure 9b, as the plunger 154 is lowered to compress the tubing portion 132, an outward surface 157 of the flange will contact an upper surface 131 of the anvil 156, preventing the plunging portion 161 of plunger 154 from continuing further downward into the tubing portion 132. The dimensions of the plunger 154, flange 155 and anvil 156 can be configured such that the farthest the plunger 154 is allowed to travel downward is just sufficient to cease flow through the tubing portion 132 or to limit the flow through the tubing portion 132 to a desired lower limit. This ensures that the tubing portion 132 will not be overcompressed, which results in a longer usable life for the tubing portion 132 and prevention of premature failure.

Manufacture, assembly, and repair of flow controllers are also simplified by the present design. Main body portion 102 can be formed of a generally rectilinear fluoropolymer, such as PTFE, with the sensor apertures 124, pinch aperture 128, flow path 1 16, integral connections and fittings and removable portion 130 formed therein. The additional components can then be assembled with main body portion as depicted in Figures 2a and 2b and described herein. Repair of variable valve portion 108 can be easily accomplished by removing removable portion 130.

The present invention may be embodied in other specific forms without departing from the spirit of any of the essential attributes thereof. Therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.

Claims

1. A flow controller for use with a fluid flow circuit conveying a process fluid, comprising: a body portion including a fluid flow passage extending therethrough and a fluid inlet and a fluid outlet in communication with the fluid flow passage;

a variable valve portion, the variable valve portion including a removable flexible hollow tubing portion in fluid communication with one of the fluid inlet or the fluid outlet of the body portion at a first end of the tubing portion and having a fluid inlet or fluid outlet on a second end of the tubing portion;

a flow measurement portion disposed in conjunction with the fluid flow passage for determining the fluid flow in the fluid flow passage;

a motor assembly including a motor and a tubing pincher, the motor actuatable to adjustably move the pincher between a first position and a second position in a direction generally transverse to the tubing portion of the variable valve portion, and wherein when the plunger is in the first position fluid can flow freely through tubing portion and when the pincher is in the second position the plunger engages the tubing portion to limit flow of the fluid through the tubing portion; and

wherein the fluid inlet, the fluid outlet, the fluid flow passage, and the flexible hollow tubing are all collinear.

2. The flow controller of claim 1 , wherein the flow measurement portion comprises a pair of pressure sensors each of the sensors having a sensing chamber positioned in the body portion with the flow passage therebetween.

3. The flow controller of one of claims 1 or 2, wherein the fluid flow passage intermediate the pair of pressure sensors has a constant diameter within 5 percent of the largest diameter of the fluid flow passage.

4. The flow controller of one of claims 1 or 3, wherein the tubing portion of the variable valve portion has a constant diameter.

5. The flow controller of one of claims 1 through 4, wherein the fluid flow passage and the tubing portion are linearly aligned with each other.

6. The flow controller of any of claims 1 through 5, wherein the body portion includes a removable portion that encloses the variable valve portion and is removable to provide access to the variable valve portion.

7. The flow controller of any of claims 1 through 6, wherein the pincher limits the fluid flow through the tubing portion by pinching the tubing portion against an anvil portion of the removable portion.

8. The flow controller of any of claims 1 through 6, wherein the motor comprises a linear actuator stepper motor.

9. The flow controller of claim 1 , wherein in the second position the pincher engages the tubing portion to stop fluid flow through the tubing portion.

10. The flow controller of one of claims 1 through 9, wherein the body portion is formed of a fluoropolymer.

1 1. The flow controller of one of claims 1 through 10, further comprising an electronic control portion and wherein the motor is actuated by the electronic control portion.

12. The flow controller of claims 1 through 1 1 , wherein there is a pair of pressure sensors disposed in sensor apertures in the main body portion, and the fluid flow passage, fluid inlet and outlet, and sensor apertures are formed in a unitary main body portion whereby there are no connections between any of the sensor apertures, the fluid flow passage and the fluid inlet and outlet.

13. The flow controller of one of claims 1 , 9 or 10, wherein the pincher comprises a flange and a plunging portion extending from the flange that engages the tubing against an anvil portion of the removable portion in the second position, and wherein, in the second position, the flange of the pincher engages an outwardly facing surface of the anvil positioned closer to the plunger than the tubing portion to prevent the plunging portion from extending further into engagement with the tubing.

14. A method of allowing fluid to flow through a flow circuit, comprising: connecting a fluid source to an inlet side of a flow controller having a body portion with a fluid flow passage extending therethrough, the flow controller further including a variable valve portion including a removable flexible hollow tubing portion in fluid communication with the fluid flow passage and a motor assembly including a motor and a plunger;

connecting an outlet side of the flow controller to a fluid receiving device;

activating the fluid source to allow fluid to flow into the inlet side of the flow controller, through the fluid flow passage of the body portion and the tubing portion of the variable valve portion, and out the outlet side of the flow controller into the fluid receiving device;

receiving an indication of a pressure drop of the fluid as it flows through the fluid flow passage transmitted by a pressure sensor disposed within the body portion; and

selectively actuating the motor assembly to move a tubing pincher to pinch the tubing portion of the variable valve portion, thereby limiting the flow of the fluid through the tubing portion.

15. The method of claim 14, wherein the fluid flow passage has a constant diameter.

16. The method of one of claims 14 or 15, wherein the fluid flow passage and the the tubing are linearly aligned.

17. The method of claim 14, further comprising:

deactivating the fluid source to cease fluid flow into the flow controller; and

removing a removable portion of the body portion to access the variable valve portion.

18. The method of claim 17, further comprising disconnecting the tubing portion from communication with the fluid flow passage.

19. The method of claim 17, wherein the step of selectively actuating the motor assembly to engage the plunger with the tubing portion of the variable valve portion limits the fluid flow through the tubing portion by pinching the tubing portion against an anvil portion of the removable portion.

20. The method of claim 14, wherein the step of selectively actuating the motor assembly to engage the plunger with the tubing portion of the variable valve portion includes engaging the plunger with the tubing portion to prevent fluid from flowing through the tubing portion.

21. The method of claim 14, further comprising calibrating the flow controller to provide a desired pressure drop to the fluid as it flows through the flow controller.

22. The method of claim 14, further comprising engaging a flange of the plunger with an outwardly facing surface of an anvil portion against which the tubing portion is engaged to prevent further movement of the plunger into engagement with the tubing portion.

23. A flow controller for use with a fluid flow circuit conveying a process fluid, comprising: a pair of external connectors for connection of the fluid controller to fluid flow circuit; a flow measurement portion having a fluid flow passageway, the flow measurement portion connected to at least one of the external connectors;

a variable valve portion, the variable valve portion including a pair of internal connectors and a removable flexible hollow tubing portion in fluid communication with the flow measurement portion connected between the internal connectors;

wherein the pair of external connectors, the internal connectors, the flexible hollow tubing and the fluid flow passageway are all collinear.

24. A flow controller for use with a fluid flow circuit conveying a process fluid, comprising: a pair of external connectors for connection of the fluid controller to fluid flow circuit; a flow measurement portion having a fluid flow passageway, the flow measurement portion connected to at least one of the external connectors;

a variable valve portion, the variable valve portion including a pair of internal connectors and a removable flexible tubing portion in fluid communication with the flow measurement portion connected between the internal connectors;

wherein the only connections within the flow controller are at the internal connectors connecting to the flexible tubing.

25. The flow controller of claim 24 wherein the pair of external connectors, the internal connectors, the flexible hollow tubing and the fluid flow passageway are all collinear.

26. The flow controller of claim 24 or 25, further comprising a unitary main body portion with a pair of pressure sensors disposed in sensor apertures in the main body portion defining a pair of sensor chambers, and the fluid flow passage extending between the pair of sensor chambers.

27. The flow controller of any of claims 24 through 26 wherein the variable valve portion comprises a tubing pincher engaged with the flexible tubing.

28. The flow controller of claim 27 further comprising a motor controller and a motor connected to the tubing pincher.